Oil and gas wells, typically, are completed for production by installing a well packer in a well bore to seal with the wall of the well bore or a well casing installed in the well bore. A well production tubing string is then coupled at a lower end into the well packer to conduct oil and/or gas to the surface. The packer seals the annulus in the well bore around the tubing string so that well fluids entering the well bore below the packer are directed into the tubing string to the surface and excluded from the annulus above the packer within the well bore around the tubing string. The packers may be installed using wireline-set, tubing-set, or hydraulic-set equipment and techniques. The production tubing strings may be run with the packer or after the setting of the packer, depending upon the equipment and techniques employed. The production tubing strings are ordinarily releasably coupled along a lower end into the bore of the well packer. A seal unit secured on the lower end of the production tubing sealingly engages the bore of the packer. Where the packer has a receiving head including one or more internal latch lugs, the seal unit may be equipped with a locator body having a J-slot configuration or a straight-slot arrangement. When using a J-slot, the seal unit is securely anchored into the packer so that tension can be applied to the tubing string and rotational torque can be applied to activate a device rotationally while the lower end of the tubing string is anchored. As the J-slot positively locks with the packer lug, it can be determined at the surface when the seal unit is landed and locked with the packer. The positive latch with the packer provided by the J-slot connection has disadvantages, however. Well conditions may develop where heat causes expansion of the production string. An acidizing operation where the tubing is washed down with acid may cause the tubing to contract. Under either circumstance, having a tubing positively latched into the packer may result in destruction of a portion of the coupling between a tubing and a packer. The straight-slot coupling between a seal unit and a packer head provides for torque transfer from the tubing string and allows the tubing string to contract and extend longitudinally, but provides no positive indication of when the seal unit has landed when it is raised after landing in the packer head.
One prior art packer having a receiving head with a latch lug is a type WB Otis Engineering Corporation Packer illustrated at page 14, of the Otis Engineering Catalog No. OEC5120D, published in 1982. Also, shown in such catalog at page 27, are Otis Sealing Assemblies having J-slot and straight-slot locator bodies. Another form of seal assembly shown at page 51 of such Otis Engineering Corporation catalog is a collet-type latch which utilizes radially movable collet fingers having collet bosses which latch in a recess in the packer providing an indication when the seal assembly is latched into the packer, but not permitting either longitudinal movement of the tubing string responsive to expansion and contraction of the tubing or rotation of the tubing string when desired or torque transfer to a packer.
Examples of the use of collet assemblies for connection of a production tubing string into a packer head and body are shown in U.S. Pat. No. 4,570,707 issued Feb. 18, 1986, to John R. Setterberg, Jr. and in U.S. Pat. No. 4,289,202 issued Sept. 15, 1981, to William D. Henderson. A well packer having a head or top sub equipped for operation with a seal unit of the present invention is illustrated and described in U.S. Pat. No. 4,441,553 issued Apr. 10, 1984, to John R Setterberg, Jr., and Dhirajlal C. Patel.